J. Raptor Res. 49(2):141–151 E 2015 The Raptor Research Foundation, Inc. PREY USE AND PROVISIONING RATES OF URBAN-NESTING MISSISSIPPI KITES IN WEST TEXAS BRANDI C. WELCH1 Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409 U.S.A. CLINT W. BOAL U.S. Geological Survey, Texas Cooperative Fish and Wildlife Research Unit, Texas Tech University, Lubbock, TX 79409 U.S.A. ABSTRACT.—Urban ecosystems are attractive to several raptor species, including the Mississippi Kite (Ictinia mississippiensis). To better understand the niche filled by urban-nesting Mississippi Kites, we observed nesting kites at 10 nests for a total of 269 hr during the breeding seasons of 2010 and 2011. We assessed prey delivery rates and prey use within and between years, evaluated the influences of nestling age, time of day, day of year, and local atmospheric conditions on delivery rates, and examined provisioning rates by male and female kites. A 62% decrease in the prey delivery rate, measured by the number of prey deliveries, from 2010 to 2011 was likely attributable to extreme heat and drought during the 2011 breeding season. However, total biomass of identified deliveries increased 38.9% in 2011 due to an increase in the percent- age of avian prey (from 1% to 16% of identified deliveries). We suspect that differences in weather conditions between years influenced the type of prey delivered, and our modeling efforts indicated that year, nestling age, time of day, and temperature best explained the number of prey deliveries made per hour. On average, females delivered more prey items than males, but variability among nests suggested additional factors may influence parental effort. Our results suggest that Mississippi Kites exhibit prey switching under differing conditions. KEY WORDS: Mississippi Kite; Ictinia mississippiensis; diet; nesting; parental care; prey; provisioning rates. USO DE PRESAS Y TASAS DE APROVISIONAMIENTO DE ICTINIA MISSISSIPPIENSIS NIDIFICANTES EN AMBIENTES URBANOS EN EL OESTE DE TEXAS RESUMEN.—Los ecosistemas urbanos resultan atractivos para varias especies de aves rapaces, incluyendo a Ictinia mississippiensis. Para entender mejor el nicho que ocupan los individuos de I. mississippiensis que nidifican en ambientes urbanos, observamos individuos reproductivos en 10 nidos durante un total de 269 horas en las e´pocas reproductivas de 2010 y 2011. Estimamos las tasas de aprovisionamiento de presas y el uso de presas dentro y entre los an˜os de estudio; evaluamos la influencia de la edad de los pollos, la hora del dı´a, el dı´a del an˜o y las condiciones atmosfe´ricas locales en las tasas de aprovisionamiento; y examinamos las tasas de aprovisionamiento de machos y hembras. La disminucio´n en un 62% de la tasa de aprovisionamiento de presas entre el an˜o 2010 y el 2011 medida como el nu´mero de presas aportadas, se debio´ probablemente al calor extremo y a la sequı´a durante la e´poca reproductiva del 2011. Sin embargo, la biomasa total de las presas aportadas identificadas aumento´ un 38.9% en 2011 debido al incremento en el porcentaje de presas en forma de aves (de 1% a 16% de los aportes identificados). Sospechamos que las diferencias interanuales en las condiciones climatolo´gicas influenciaron el tipo de presa aportada y nuestros modelos indican que el an˜o,la edad del pollo, la hora del dı´a y la temperatura fueron los para´metros que mejor explicaron el nu´mero de presas aportadas por hora. En promedio, las hembras aportaron al nido ma´s presas que los machos, pero la variabilidad entre los nidos sugiere que otros factores pueden estar influyendo en el esfuerzo parental. Nuestros resultados sugieren que I. mississippiensis cambia sus presas bajo condiciones diferentes. [Traduccio´n del equipo editorial] Habitat modification from natural to urban areas Compared to undeveloped landscapes, urban eco- is a common trend worldwide (Grimm et al. 2000). systems tend to promote occupancy by a greater density, but reduced diversity of species (Clergeau 1 Email address: [email protected] et al. 1998). In an early urban wildlife study, Emlen 141 142 WELCH AND BOAL VOL. 49, NO.2 (1974) found that granivorous, nectarivorous, and rado, Kansas, Nebraska, and Oklahoma (Bolen and insectivorous birds could be supported in urban en- Flores 1993). Previous researchers suggest that ex- vironments. Later studies, however, demonstrated pansion was facilitated by human-mediated vegeta- that urban ecosystems were also attractive to several tion changes as the Southern Great Plains were raptor species (see Bird et al. 1996, Mannan and settled, resulting in subsequent changes in the dis- Boal 2004 for reviews). tribution and abundance of prey species and suit- There are several possible reasons why some rap- able nesting sites (Bolen and Flores 1993). Missis- tor species thrive in urban areas. Urban raptors may sippi Kite populations nesting on the Great Plains benefit by having a lower abundance of predators currently concentrate in urban and semiurban and reduced human persecution (Mannan and Boal areas, often nesting on golf courses, college cam- 2004). Urbanization-mediated changes in the struc- puses, or in city parks (Parker 1999, Skipper 2013). tural diversity of a landscape may be attractive and Limited information is available on how environ- promote settling by some raptors. For example, ur- mental conditions or time of day may influence the banization in arid or agricultural regions may result feeding ecology and reproductive behaviors of this in the provision of suitable nesting sites through the primarily insectivorous raptor (Parker 1999, Chia- introduction of taller woody plant species (Boal and vacci et al. 2014). Temporal and spatial aspects of Mannan 1998, Rottenborn 2000, Skipper 2013), and their foraging behavior are likely dictated by their increased abundance or availability of food and wa- invertebrate prey species, such as cicadas (Hemi- ter (Mannan and Boal 2004). Indeed, some raptor ptera) and grasshoppers (Orthoptera), which ex- species that colonize urban areas show increased hibit behavioral responses to changes in weather reproductive success that is nearly double that of and time of day (Pfadt 2002). Parental foraging be- conspecifics in rural areas (Parker 1996, Smith haviors of Mississippi Kites also change with nestling 2010). However, human activities occurring in age (Bolen and Flores 1993). Glinski and Ohmart close proximity to nests may increase mortality if (1983) identified seasonal changes in the types of birds begin to lose their instinctive fear of humans. prey delivered, but did not examine prey delivery Though some degree of habituation to humans rate in context of time of day or environmental con- may be necessary for urban birds to carry out daily ditions at nonurban Mississippi Kite nests in Ari- feeding or resting activities, it may also make them zona. Botelho et al. (1993) correlated prey delivery more susceptible to human persecution (Whittaker rate with nestling age at a single urban Mississippi and Knight 1998). In addition, noise generated Kite nest in New Mexico, but the inferential value of from nearby roadways and other sources may hin- the study was limited by the sample size. Sex-specific der communication between individuals by de- differences in the types of prey delivered and creasing the distance that auditory signals (e.g., changes in diet associated with nestling age and alarm calls, contact calls) can be perceived (Barber environmental conditions were assessed via video et al. 2010), and increased exposure to disease in recording at kite nests in swamplands of eastern urban landscapes can lead to decreased reproduc- Arkansas (Bader and Bednarz 2011, Chiavacci et tive success (Boal et al. 1998, Boal and Mannan al. 2014). Ultimately, despite their relative abun- 1999). Yet, in studies of urban-dwelling raptors, dance, little quantitative data are available describ- an apparent positive relationship between prey ing the food habits and breeding ecology of Missis- abundance and reproductive success (Newton sippi Kites, and except for the limited New Mexico 1998) seems to explain higher reproductive perfor- study (Botelho et al. 1993), no data are available for mance in urban compared to rural settings (Smith urban-nesting kites. 2010). We examined the breeding ecology and food ha- Mississippi Kites (Ictinia mississippiensis) may be bits of Mississippi Kites in Lubbock, Texas, during the most abundant urban-nesting raptor in the the breeding seasons of 2010 and 2011. The objec- United States (Parker 1996). Prior to the early tives of our study were to (1) assess prey delivery 20th century, breeding Mississippi Kites were distrib- rates, (2) develop an understanding of parental uted from eastern Texas to South Carolina, and roles and changes in parental care with nestling along the Mississippi Valley as far north as Iowa age, and (3) examine the influence of weather con- (Parker and Ogden 1979). The distribution of the ditions and time of day on the rate of prey delivery species has since expanded westward to Arizona and (items/hr) and prey type delivered to nestlings by northward into the Southern Great Plains of Colo- urban-nesting Mississippi Kites. JUNE 2015 URBAN MISSISSIPPI KITES IN TEXAS 143 METHODS from the nest tree. Observation points were located Study Area. We conducted our study in Lubbock, under the concealment of nearby vegetation and Texas, (population 236 065; City-Data 2013) located a large umbrella positioned by the observer. At no on the Southern High Plains region of western Tex- time during observations did any kite appear to dif- as and within the southernmost portion of the Great ferentiate the observers’ presence from the normal Plains. Lubbock is 922 masl, receives an average foot traffic in the study area. annual precipitation of 47.5 cm, and has average We identified prey during direct observations high temperatures ranging from 11.1uC in January when possible and subsequently confirmed identifi- to 33.3uC in July.